This project will test the ependyma-mesenchyme hypothesis of spinal cord regeneration. This hypothesis maintains that the connective tissue environment of the wound area is of prime importance in determining whether or not spinal cord regeneration will occur. In the lizard, Anolis, ependymal growth and morphogenesis, including central fiber regeneration and fasciculation by the ependyma occurs during tail regeneration. Ablation of the spinal cord at mid-trunk levels results in no regenerative response. The wound connective tissue that develops at the two sites is very different. Autografts of tail blastema tissue will be made to ablation sites in the mid-trunk cord in an attempt to stimulate ependymal cell proliferation and morphogenesis of the epithelium. Preliminary experiments suggest that the differences in response at the two levels is not due to intrinsic differences in the spinal cord at the two levels. The mature adult ependymal epithelium can be obtained as a pure population of epithelial cells. Explants of pure ependymal epithelium will be challenged in culture with appropriate embryonic mesodermal tissues (both lizard and chick) to evaluate the ability of the mature ependyma to produce neurons and glia in response to normal developmental signals. This study will make use of microsurgery, grafting of tissue and of cultured cells, horseradish peroxidase tracing of regenerated central fibers, Bodian silver staining, transmission electron microscopy and organ culture techniques. Basic information provided by the proposed study will enhance our chances of designing realistic, rather than ad hoc, approaches to engineering spinal cord regeneration in mammals, including humans.